Radiation therapy treatment devices deliver radiation to a patient in multiple treatments, each of which is called a fraction. In conventional fractionated therapy (FT), a standard radiation therapy protocol, the total prescribed dose of radiation is divided into equal fraction sizes that are delivered to a patient at discrete times over the course of treatment (e.g., over a period of weeks rather than in a single session). The purpose of fractionation is to increase normal tissue sparing while simultaneously maintaining the same level of tumor cell kill, thereby increasing the therapeutic ratio. Fractionation therapy usually results in a better therapeutic ratio than single session therapy because it spares more normal tissue through repair of sub-lethal damage between dose fractions and repopulation of cells. Concurrently, FT increases tumor damage through reoxygenation and redistribution of tumor cells. The number of fractions and resulting dose per fraction are determined during the planning procedure prior to treatment in conventional FT. A typical radiotherapy treatment course consists of 30 to 40 fractions, with the predetermined fraction size (e.g., 2 Gy/fraction) used throughout the treatment.